Low levels of B vitamins in breastfeeding mothers can translate into low levels in their babies, and may slow growth in the early stages of life.

That's the conclusion of a paper analyzing the scientific research on the topic by Lindsey H. Allen of the U.S. Department of Agriculture. A lack of data places some limits on these conclusions, as much of the evidence is from the world's poorest areas where malnutrition is prevalent. But the overall picture points to an urgent need to improve the information available on breast milk quality.

Poor maternal status of thiamin, riboflavin, vitamin B-6, vitamin B-12, and choline, causes the concentrations of these nutrients to be low in breast milk and the infant to become deficient.

Mothers with a low intake of animal source foods are at higher risk of nutrient deficiency, especially for riboflavin and vitamin B-12. Inadequate intake of thiamin and vitamins B-6 and B-12 could contribute to reducing babies' growth in the first year of life.

Taking supplements during lactation rapidly increases the concentrations of thiamin, riboflavin, and vitamin B-6 in milk, but increases in vitamin B-12 levels are small even when high doses are given to the mother for 2 months.

The first month of a baby's life is thought to be a special period of vulnerability to vitamin B12 deficiency as it can be linked to poor neurodevelopment and slow growth.

Nutrient deficiency is usually not an issue for mothers consuming a healthy diet, but since animal products are the main dietary source of Vitamin B-12, vegetarians should be careful about deficient vitamin B-12 levels.

“Uncertainty over the nutrient composition of breast milk is what led me to develop a test for exactly what is in it,“ said Lactation Lab founder Stephanie Canale, M.D.

"While breast milk of mothers consuming a healthy diet is typically nutritious, special diets and other factors can result in less than optimal nutrition for the baby. Lactation Lab’s test kits and followup recommendations are designed to help ensure that a mother’s breast milk is the best it can be.”

Mothers who are concerned about the nutrient composition of their breast milk can use Lactation Lab's test kit to find out whether they need to adjust or supplement their diet.